By Emily Manley

By now, we mostly know the rules of eating locally: Eschew the apples grown halfway across the world and bite into a local variety instead. Forget the mysterious mass-produced milk in plastic jugs and go for the stuff bottled at nearby dairy farms.

But what happens when you wash it all down with a big glass of…French wine?? Do you know the carbon footprint of your vino?

Put a Cork in Your Carbon

It turns out that just like fruits and vegetables, wine also has a carbon footprint, albeit one with a lot of variables.

Wineries can now be found across the globe — from Chile to China — and in 48 of the 50 United States. It’s grown organically, biodynamically and conventionally, packaged in bottles, magnums and boxes, and transported on ships, planes, trucks and trains.

Which makes for some confusing carbon footprint calculations.

Luckily there are easy things we can all do to shrink our wine-drinking carbon footprint — and people to tell us just how to do it.

Tyler Colman, New York University professor and writer for the blog Dr.Vino, and his colleague, Pablo Paster, spent a few months last year studying the carbon footprint of wine — specifically how much carbon is emitted during a wine bottle's journey from vineyard to retail.

What they found just might surprise you...

Walk the Line

While “food miles” (the distance food travels from the time of its production until it reaches the consumer) are important, not all of those miles are created equal when it comes to wine production.

Efficiencies in transportation make container ships better than trucks, which in turn are better than planes.

By calculating the mileage and transportation involved in getting your wine to you, Colman found that there exists a “green line” running smack down the middle of Ohio:

• Live on the east side of that line, and it’s more carbon-friendly to get your wine from states on the East Coast or from Europe (more efficient container shipping and a shorter truck trip compensate for the distance).
• Live on the west side of the line, and you should start getting to know the vintners in California, Oregon and Washington.

Avoid a Carbon Hangover

While climate change does pose a threat to the ancient art of grape growing and wine making around the world, it's important to remember that there are things we can all do to make a difference.

Whether you live on the West coast or the East — and whether you prefer Pinot Noir or Sangiovese — the choices you make today could influence the wines you drink tomorrow.

Remember these important facts the next time you visit your local wine merchant:

1. Stay Close to Home: Most carbon emissions from wine are a result of transportation. Choose the vintage closest to home that has arrived in the most energy efficient manner. Out of the three, container shipping is the best, plane travel is the worst and trucking falls somewhere in the middle.
2. Walk the Line: If the wines from your home state don't pass your muster, try using Colman's "green line" calculations as a reference before making your purchase.
3. Go Natural: Organically or biodynamically produced wine is easier on the Earth and less carbon-intensive. Ask around at your local wine shop to see which vineyards practice organic wine making.
4. Offset: Worried about your own carbon footprint? Want to do more? Add up your own carbon emissions using our handy carbon calculator — and then find out ways to offset your impact.

Emily Manley is a marketing specialist for The Nature Conservancy in New York.

Nature picture credits (left to right): © Gabor Izso (Grapes on a vine); © Tyler Colman (map); © iStockPhoto.com (King Protea flower, Australia)